Central Auditory Processing Disorder by Rosalie Seymour
The subject of auditory processing is still a controversial one, with most professional service providers and diagnosticians being uninformed on the matter. Speech therapists and audiologists have gained the use of more sophisticated assessment tools, but are for the most part uneasy about involvement with this topic for a variety of reasons.
However, the demand for services is on the increase, and FST / AIT practitioners are becoming more and more aware that their intervention could have a significant impact in this area, as the focus of our attention broadens to include more than just hyperacusis and peaks in the hearing test.
Questions and Answers
Q. Definition of CAPD
Jack Katz defines AP as “ What we do with what we hear”. Once the ear has heard a sound (audition), before it can be understood (conceptualisation), the input must be;
- located (localisation)
- attended to (auditory awareness and vigilance)
- differentiated (including background / foreground separation)
- coordinated with other sensory input
“An AP problem is present when a person is not able to make full use of the heard signal” (Katz).
This in-ability can lead to scholastic underachievement.
An AP disorder is likely to have personal and social impacts as well.
APD may be present in a mild form, or in a severe form.
APD may be present together with a hearing loss, and also without the presence of a hearing loss. Any other condition may coexist with APD, e.g. learning disability, cerebral palsy, Down syndrome, and so on.
APD has been associated with specific learning disabilities/ dyslexia since 1932 (Monroe). Orton (1964) and Sawyer (1981), Bannantyne (1969) Tomatis (1954), and Tallal (1976), are among the many who investigated this link. In addition, these children may demonstrate other characteristics;
- visual processing deficits
- motor problems
- balance and other deficits
These children and adults have problems with;
- following directions
- processing speed
- localising a sound source
- listening against a noisy background (refer to the IELP Auditory Problems Checklist ,1997)
In addition, these children have often come to the notice of school staff in a negative way – being at the centre of disturbances, for inappropriate and rude behaviour, for disobedience. All these behaviours can be the direct result of APD, and proper identification and information can remove the stigma as staff, parents and the child better understand the problem.
The incidence of conductive hearing loss is high in pre-school and primary-school-age children, due to the prevalence of otitis media(O-M) in this population. This condition (O-M) is now known not to be the benign condition it was once believed to be. Whether the condition is inflammatory, infectious, or whether there is simply an a-symptomatic effusion, the conductive hearing loss associated with this condition has, in many cases, a lasting effect on the Central Nervous System(CNS) organisation of AP. The term Central APD (CAPD) is often used to emphasise that the disorder is in the brain’s ability to “work with” sound , and not in the ear’s ability to receive sound.
Children with a fluctuating hearing loss (as a result of recurrent ear-infections ) are considered to be at-risk for language, speech and learning problems. A threshold shift of 15 dB is significant as a handicapping loss for a young child, even if it is a unilateral loss. (Katz). Drs Northern and Downs (1991) state that this effect is especially severe if the fluctuating hearing loss occurred in the first year and a half of life!
Q. Identifying CAPD
The aim of attempting to identify APD is to find out to what extent it handicaps or restricts the person. The audiologist may be one of the first professionals called in to assess the difficulty.
The pure-tone threshold assessment is the standard beginning, and in audiological procedures, other assessments may follow, e.g.:
- the bone conduction evaluation. This is especially important when a hearing loss is evident
- word discrimination and speech reception threshold
- immittance audiometry, acoustic impedance, & reflex thresholds
- the Staggered Spondaic Words test (SSW)
- Competing Sentences Test (CST)
These yield valuable insights into the significance of the APD in the individual’s functioning.
Physiological measures can yield valuable information regarding CAPD, and is especially useful to convince sceptics. Auditory Brainstem Response (ABR), Middle Latency Response(MLR), and Long Latency Response(LLR) testing tell us about the area between the VIII cranial nerve end and the temporal (auditory) cortex. MLR and LLR especially give information about the central processing areas of the brain. The ABR gives brainstem-information, chiefly. In 1990, Jirsa and Clontz studied LLR, and found longer latencies in the experimental group for N1 and P2, and P3. There was also considerable LLR variability for this group.
These assessments may yield interesting results for research purposes. They are not commonly available to clients, however, and the cost involved, and the invasiveness of some of these procedures make them inappropriate for routine evaluations. Since the aim of evaluation is, as stated by J.Katz and others, to determine the implications of the CAPD on the child’s life experiences, and to point the way towards intervention,- a strong argument may be made for the use of less invasive and less expensive assessment tools.
The “battery” that fits this requirement, could effectively consist of:
- An Auditory Problems Checklist
- The Bérard Listening Tests
- A case history
In 1976 Fischer published the Auditory Problems Checklist that is useful to identify potential CAPD’s. Willeford and Burleigh’s scale (the Willeford and Burleigh Behaviour Rating Scale for Central Auditory Disorders), and Smoski et al published the CHAPPS. These are useful to school personnel as well.
Similar to these, the IELP Auditory Problems Checklist yields valuable behavioural indicators, especially if completed by the teacher and the parents.
Dr. Bérard’s hearing assessments include;
- the listening test, using pure tones
- the test for laterality
- the test of selectivity.
The above tools, with the case history, yield a valuable profile of the impact of the child’s CAPD on his life and learning. Sometimes there may be a need to ensure that thorough testing is done, since the presence of a CAPD could be masked by many factors e.g. emotional, intellectual, and inaccurate reporting by both parents and teachers, as well as the presence of a hearing loss. In these cases, referral to an audiologist is advised; if possible, one who is familiar with FST / AIT and is comfortable with assisting the practitioner.
The speech therapist may perform a collection of assessments, covering areas of
- speech sound discrimination
- memory for digits memory for words, or syllables
- memory for sentences
- memory for story
- symbol-to-sound association
- auditory analysis and synthesis
- sound blending
- auditory closure
- vocabulary comprehension
- linguistic competence (reception, and use)
- word-finding ability
Where these tests are performed on a yearly basis, as they are at some remedial schools, the results can provide useful material as a record of progress after FST / AIT.
Q. Classroom Management
Before the advent of FST / AIT as an intervention option, management was best done by
- Changing and managing environmental factors to provide the easiest listening environment during the school day by reducing background noise and enhancing the foreground speech.
- Teaching the skills and strategies to deal with the listening task.
Q. Mechanical Aids
Besides these traditional approaches to management of CAPD, there have been various mechanical devices to assisting these children in classroom situations. These are known as Assistive Listening Devices, usually minimal gain FM systems. The most well-known is the Phonic Ear ©.
This device acts as a sound-boosting system, making the teacher’s voice louder for the child, i.e. improving the signal-to-sound ratio. It is found to be quite helpful, but only in the classroom situation.
When the child is in play, or at sports, or at home, this system cannot be used, and the child still suffers the effects of this APD in his everyday life situations. It would be more helpful to the child if one could alter his problematic listening mechanism, rather than merely support it.
Q. Filtered Sound Training / Auditory Integration Training
Happily, there is now a way to do this. Since the advent of the Bérard approach to auditory training, with the further development of the home-delivered pc-based system known as Filtered Sound Training (FST), children and adults with symptoms of APD are finding improvements in their ability to ‘work with sound’.
These improvements are seen after a simple 10-day auditory stimulation period using specially-filtered and altered sounds in music.
The kinds of benefits are listed in the many research reports (see below) as well as reports by parents and therapists.
Opposition to this approach has been sporadic, while the Speech and Audiology therapists have been more heated in their disapproval, in spite of the positive research and client feedback. Lately many of these professionals are beginning to admit to the benefits of this approach, and are becoming more involved in its practice. (see research reports at AIT Institute)
Meanwhile, clients who seek out this training are contacting practitioners through word-of-mouth and information available on the websites.